Electrochromic VLTPs with Interference Stack for Uniform Appearance
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Solution Overview
Problem
Variable light transmission panels (VLTPs) with electrochromic technology change their optical state in response to electrical stimuli, causing undesirable external appearance changes when viewed from outside, leading to a 'checkerboard effect' due to differences in light transmission properties, which affects the aesthetic uniformity of buildings and vehicles.
Innovation Solution
The use of a specific configuration of electrochromic variable light transmission panels with two transmissive substrates, a coating stack including a transparent conductor and an electrochromic layer, and an electrolyte layer, optimized to minimize color differences in reflection and transmission, ensuring a uniform appearance even when in different optical states, achieved through the incorporation of an interference stack and low-e coatings in insulated glass units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If electrochromic variable light transmission panels are used to regulate solar energy penetration, then energy efficiency and comfort are improved, but the external appearance changes when viewed from outside, causing a checkerboard effect
Solution Approach 1:
The patent applies color change technology by incorporating an interference stack with multiple dielectric layers that create wavelength-selective reflection. This stack is designed to reflect specific wavelengths (e.g., red, green, blue) to dominate the external appearance, masking the color changes of the electrochromic layer while allowing full light transmission modulation. The interference stack maintains a substantially constant appearance from the outside regardless of the electrochromic layer's optical state.
Solution Approach 2:
The patent creates a composite structure combining the electrochromic layer with an interference stack of multiple dielectric layers. This composite material approach allows the system to simultaneously achieve variable light transmission (from the electrochromic layer) and constant external appearance (from the interference stack), resolving the contradiction between energy efficiency and appearance uniformity.
2Ease of operation
If the light transmission properties of windows are changed to provide shade and glare reduction, then indoor comfort is improved, but the exterior appearance of the window changes, resulting in a checkerboard effect
Solution Approach 1:
The interference stack is designed to produce strong wavelength-selective reflection that dominates the external appearance. By carefully selecting the refractive indices and thicknesses of the dielectric layers, the stack reflects specific wavelengths that create a consistent visual appearance regardless of the electrochromic layer's transmission state, thereby maintaining exterior appearance uniformity while enabling indoor comfort control.
Solution Approach 2:
The patent addresses the appearance issue by adding another dimension to the optical system - the interference stack operates in the reflection dimension while the electrochromic layer operates in the transmission dimension. This dimensional separation allows independent control of external appearance (reflection) and internal comfort (transmission), resolving the contradiction between these two requirements.
3Loss of energy
If variable light transmission panels are used to control solar energy penetration, then energy savings are achieved, but the windows in different optical states lead to differences in appearance when viewed from outside
Solution Approach 1:
The interference stack is engineered to produce wavelength-selective reflection with high intensity, causing the reflected color to dominate the external appearance. The stack's optical design ensures that the reflected wavelengths mask any color changes in the transmitted light, maintaining appearance consistency while enabling full energy savings through electrochromic modulation.
Solution Approach 2:
The patent changes the optical parameters of the window system by introducing an interference stack with specific refractive index profiles and layer thicknesses. This parameter change creates a new optical regime where reflection dominates appearance perception, allowing the system to achieve energy savings through transmission control without compromising appearance consistency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures that the external appearance of buildings and vehicles remains largely unchanged during the day, even when the VLTPs transition between different optical states, maintaining a uniform appearance and allowing for customizable internal light transmission while minimizing external color and reflectivity changes.
Implementation Method 1
When electrically controlled VLTP devices are fabricated using transparent substrates, these devices upon application of an electric voltage change their optical state, i.e., color, opacity, and/or transparency (light transmission or reflection)
Implementation Method 2
the first substrate having two sides wherein the second side is coated with a coating stack comprising of at least two layers, followed by a coating of a transparent conductor
Implementation Method 3
the IGU assembly contains at least one low-e coated panel in addition to the VLTP
Data Source
AI summary
This disclosure includes variable light transmission panels (VLTPs) and their assembly into insulated glass units (IGUs), which can be incorporated into buildings. Disclosed windows provide uniform appearance from outside during the day when a number of such windows are incorporated in a building regardless of their state of light transmission. These disclosures may also be used to make windows which tint to different transmitted colors but during the day still appear to be uniform from outside.